The present invention relates to hydrofoil craft and, more particularly, to improvements in the hull of a hydrofoil craft having on the bottom one or several air cushion recesses arranged in one row or several rows along the longitudinal direction and capable of leading in pressure gas to produce an air cushion effect.
The hydrofoil craft has not always been popularly employed in a large number on sea although such craft have been known for many years. This is mainly because horse power needed to arrive at a gliding or planing state is very large and accordingly, such craft must be equipped with a motor much larger than a general ship. Again, although an air cushion craft has also been used commercially, due to the reason that the hull must utilize a rubber tent or apron to form thereinside an air cushion, the manufacturing and maintenance costs are very high and further, since there is no parts for self stabilizing and supporting and the ride quality is not excellent, the craft must be made considerably large and must sail on a relatively smooth water surface. For the foregoing reasons, it is still difficult for the craft to be used extensively as a general water transport means.
Accordingly, one object of the present invention is to provide a hydrofoil craft having on the bottom at least one row of air cushion recesses arranged in the fore-aft direction, which on gliding produces an excellent air cushion effect thereby lowering resistance of adherence on the craft bottom and achieving quickly a state of hydrofoil gliding or flight.
Another object of the invention is to provide a hydrofoil craft which offers reduced horse power requirements compared to conventional deep-V hull ships having similar payload capacities. The invention is directed to providing such a craft capable of a ship speed between 25 to 60 knots, in which acceleration is fast and ride quality is excellent. It is further an object of the invention to provide a craft which is not easily touched down by wave tips during gliding and having stability characteristics better than ships, of the same breadth.
A further object of the invention is to provide a hydrofoil craft which, when the main engine exhaust or pressure air is filled into the air cushion recesses, produces an air cushion to lift part of the ship weight and at the same time, to separate the water surface adherence side of the recesses, is capable of reducing the back pressure of the main engine to thereby increase the delivery torsion and to attain a flight state within a short time because of a vacuum phenomenon produced inside the air cushion recesses during gliding.